Chemiluminescense relates to the production of visible light attributable to a chemical reaction. The important aqueous chemiluminescence substances luminal and lucigenin were discovered in 1928 and 1935, respectively. A series of organic soluble chemiluminescent materials were developed in the early 1960's based on a study of the luminescent reactions of a number of organic compounds. A typical organic system useful for chemiluminescence was disclosed by Bollyky et al., U.S. Pat. No. 3,597,362 and claimed to exhibit a quantum efficiency of about 23% compared with about 3% for the best known aqueous systems.
In its most basic form the two-component, liquid phase oxalate ester chemical light system must comprise an “oxalate component” comprising an oxalic acid ester and a solvent, and a “peroxide component” comprising hydrogen peroxide and a solvent or mixture of solvents. In addition, an efficient fluorescer must be contained in one of the components. An efficient catalyst, necessary for maximizing intensity and lifetime control, may be contained in one of the components.
The oxalate component provides an oxalate ester-solvent combination which permits suitable ester solubility and storage stability. The peroxide component provides a hydrogen peroxide-solvent combination which permits suitable hydrogen peroxide solubility and storage stability.
The solvents of the two components may be different but must be miscible. At least one solvent solubilizes the efficient fluorescer and at least one of the solvents solubilizes the efficient catalyst.
Typical suitable fluorescent compounds for use in the present invention are those which have spectral emission falling between about 300 and 1200 nanometers and which are at least partially soluble in the diluent employed. Among these are the conjugated polycyclic aromatic compounds having at least 3 fused rings, such as: anthracene, substituted anthracene, benzanthracene, substituted benzanthracene, phenanthrene, substituted phenanthrene, naphthacene, substituted naphthacene, naphthalene, substituted naphthalene, pentacene, substituted pentacene, perylene, substituted perylene, violanthrone, substituted violanthrone, and the like. Typical substituents for all of these are phenyl, alkyl (C1–C16), chloro, bromo, cyano, alkoxy (C1–C16), and other like substituents which do not interfere with the light generating reaction contemplated herein.
The preferred fluorescers are 9,10-bis(phenylethynyl) anthracene, 1-methoxy-9,10-bis(phenylethynyl) anthracene, perylene, rubrene, mono and dichloro substituted 9,10-bis(phenylethynyl) anthracene, 5,12-bis(phenylethynyl) tetracene, 9,10-diphenyl anthracene, and 16,17-didecycloxyviolanthrone.
The term “peroxide component,” as used herein, means a solution of a hydrogen peroxide compound, a hydroperoxide compound, or a peroxide compound in a suitable diluent.
The term “hydrogen peroxide compound” includes (1) hydrogen peroxide and (2) hydrogen peroxide producing compounds.
Hydrogen peroxide is the preferred hydroperoxide and may be employed as a solution of hydrogen peroxide in a solvent or as an anhydrous hydrogen peroxide compound such as sodium perborate, sodium peroxide, and the like. Whenever hydrogen peroxide is contemplated to be employed, any suitable compound may be substituted which will produce hydrogen peroxide. The hydrogen peroxide concentration in the peroxide component may range from about 0.2M to about 15M. Preferably, the concentration ranges from about 1M to about 2M.
The lifetime and intensity of the chemiluminescent light emitted can be regulated by the use of certain regulators such as:
1) by the addition of a catalyst which changes the rate of reaction of hydroperoxide. Catalysts which accomplish that objective include those described in M. L. Bender, “Chem. Revs.,” Vol. 60, p.53 (1960). Also, catalysts which alter the rate of reaction or the rate of chemiluminescence include, but are not limited to those accelerators of U.S. Pat. No. 3,775,366, and decelerators of U.S. Pat. Nos. 3,691,085 and 3,704,231, or
2) by the variation of hydroperoxide; wherein both the type and concentration of hydroperoxide are critical for the purposes of regulation.
Of those catalysts known to be useful, sodium salicylate and various tetraalkylammonium salicylates have been most widely used. Lithium carboxylic acid salts, especially lithium salicylate, lithium 2-chlorobenzoate, and lithium 5-t-butyl salicylate are excellent catalysts for low temperature systems.
As outlined above, chemical light is produced by mixing an oxalate ester and hydrogen peroxide together in the presence of a catalyst and a fluorescer. Typically, the oxalate ester and fluorescer are dissolved in one solvent. The hydrogen peroxide and catalyst are dissolved in another. The typical chemical light device is a polyethylene or polypropylene container with the two liquids inside, separated until light is needed, for example, by packaging one of the liquids in a sealed glass vial and floating the vial in the second liquid. Light is generated when the end user flexes the plastic outer container, fracturing the glass vial or alternatively by destroying the integrity of a separating member, e.g. a diaphragm or membrane, in any suitable manner thereby allowing the two liquids to mix.
Chemical light devices are practically non-biodegradable due to the plastic utilized in their construction. Polyolefins will exist for hundreds of years in the normal environment without losing a significant portion of their physical properties. This fact has created problems and concerns in all chemical light devices markets, but especially in the military and commercial fishing markets. Additionally, the liquids inside these devices are not designed for general release into the environment. The commercially practiced solvent systems are, in fact, considered marine pollutants in many parts of the world.
Worldwide, over fifty million devices per year are consumed between the military and commercial fishing markets. This volume of consumption and the manner of the consumption is creating a waste and waste disposal problem. The permanence of the plastic container making up the chemical light devices contributes to this waste and waste disposal problem.
Military use of chemical light devices includes providing basic light (illumination), safety marking, covert marking, and as training aids. The uses often involve wide dispersion of multiple chemical light devices over large surface areas of land (many acres). After use, evidence of the military's activities are left behind (the chemical light devices) and will persist for decades or longer. Depending on where the military exercise occurs, this may not be allowed (example: USA or Europe). Military personnel are required in these areas to attempt to collect all consumed chemical light devices.
Commercial fishermen utilizing long lines to catch swordfish and some species of tuna use chemical light devices as lures or attractants. The long lines are significant in length (often miles long) and deploy thousands of hooks pendent from the long line. A chemical light device is typically attached over each hook. Therefore, thousands of chemical light devices are deployed with each long line. This style of fishing typically occurs at night, with the line deployed in late afternoon or early evening and retrieved the next morning. The commercial fishermen are encouraged to disconnect the chemical light devices and to return them to shore for proper disposal. All will disconnect the chemical light devices, but many do not return them to shore for disposal. Instead, they throw the chemical light devices overboard into the oceans. This has created a significant problem on beaches in many parts of the world, with literally thousands of plastic chemical light devices washing up onto a beach with the tides and currents.
If it were possible to provide a chemiluminescent product and chemical system which was inherently biodegradable in its environment of use, such that said device, inclusive of the chemiluminescent components, could re-enter the environment within a reasonable interval after its usefulness was at an end, then a long-felt need in the art would be satisfied.